1. Field of the Invention
The present invention relates to motors, more particularly to a compact stepping motor with a rotational position sensor.
2. Description of the Prior Art
A conventional stepping motor rotates at a constant angle corresponding to an input from a driver. A conventional motor can be controlled with high rotational position control without using a rotational position sensor such as a resolver. However, when a stepping motor is used in a vehicle application such as control of coolant, air intake and exhaust for an engine, it is necessary for the stepping motor to be accurate. Additionally, the stepping motor must also unfailingly prevent loss of control, for example, due to loss of synchronism in severe environment such as vibration during driving. Thus, in a conventional stepping motor, when used in a vehicle application, it is common to provide a rotational position sensor such as a resolver or the like, to monitor the actual rotational position of the shaft and to provide feedback to achieve accurate rotational position.
There is a need to lower the emissions and attain greater fuel economy in automobiles. As a result, automotive equipments such as engine control devices are becoming increasingly complex and sophisticated, and constraints on vehicle installation space are also increasing. Therefore, there is a need for a compact stepping motor that does not require a separate rotational position sensor and thereby reduces the demand for space. There is also a need for a low-cost, easy-to-assemble stepping motor that can withstand the severe environment such as high temperature, low temperature, dust, moisture and oil that is found in a vehicle application.